If you have a male and would like to get a female, you better plan on them mating! However, if you DO get a female, she MUST be over 18 months old... if she breeds before then it will reduce her lifespan greatly.
If you want to house two females together, make sure the cage is big enough first of all(75 gallons or larger) and that they each have a basking spot.
To introduce two dragons, you should never just simply put the new dragon in the cage. I would suggest introducing them on non-common ground... such as the floor or bath tub. This way, neither one has established any kind of dominance of the particular area. You must always be willing to intercept any kind of ''misbehaving'' though. If you are introducing a male to female, you should expect some head-bobbing or waving to happen, but if they start biting and attacking each other, seperate them immediatly. You must introduce them like this several times, and if they get along, THEN you can try housing them together. Good luck and let us all know what you decide to do!